Resistor



W. P. WILLS Dgc. 12, 1950 RESISTOR Original Filed Dec. 1, 1941 INVENTOR. WALTER P. WILLS BY 2 W\ FIG. 5

ATTORNEY Patenmi na. 12, 1950 umrsp STATES PATENT oss cs Walter P. Willa, Pa assignor, by

mesne amin'nnents, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a cor poration of Delaware 8, 1947. Divided and this 1947, Serial No. 744,213

- 6 Claims.

1 The present invention relates to variable control devices for electrical circuits, and, more especially, to an improved form of slide-wire construction having particular utility for use in and as a part of a potentiometric measuring, recording and controlling instrument.

This invention is a division of my prior application Serial No. 421,173, filed December 1, 1941, now Patent No. 2,423,540, dated July 8, 1947.

That prior application discloses electronic selfbalancing potentiometer apparatus incorporating suitable means for causing the unidirectional potentiometric unbalance currents to produce a pulsating current how of predetermined frequency in a detector circuit. The detector circuit includes an input transformer and electronic tubes for amplifying the pulsating current and for using the amplified current .to control the operation of a reversible electric motor which, for the purpose of effecting rebalance of the apparatus upon unbalance thereof, is mechanically associated with the slide-wire assembly of the potentiometer circuit. Such apparatus has particular utility for measuring thermocouple voltage and other minute voltage changes, and is well adapted to furapplication April 26,

2 wound. The collector element comprises a bare wire upon which the bare wire is space wound so that the last mentioned bare wire is electrically conductive throughout: its length with the bare wire upon which it is wound. A rotar shaft provided with an arm adiustably carried by the shaft and extending along the exterior surface of the cylindrical support is concentrically mountman an accurate measure of the magnitude, or changes in magnitude, of any measurable condition, whether mechanical, chemical, physical, etc., giving rise to a small voltage'indication of the value of the measurable condition.

Specific objects of the present invention are to provide an improved form of construction and operation of the slide-wire element per se, to provide a greater degree of convenience and efficiency of operation of the slide-wire in conjunction with the related units of 'a potentiometer instrument, and to provide a slide-wire construction in the form ofa separate slide-wire assembly complete in itself for mounting in a frame vin which other related parts, and in particular other related parts of a potentiometer instrument, may be mounted, thereby to facilitate the manufacture, assembly, and service of the slide-wire assembly unit as well as of the other related parts. I

In a preferred embodiment, the slide-wire assembly unit of the present invention comprises a cylindrical support formed of insulating material upon which is helically wound a slide-wire resistance element and a collector element arranged in side by side relation. Bare wire of substantially the same gage is space-wound upon each of said slide-wire and collector elements. The slide-wire resistance element comprises an insulated wire upon which the bare wire is spaced ed with respect to said support. In addition, a slot is provided in said arm parallel'to the axis of the cylindrical support, and'a roller is arranged for rolling movement in said slot for bridging the slide-wire resistance element and the collector element. Suitable means for rotating the shaft are also provided so that the position of the roller along the length of the slidewire and collector elements may be adjusted as desired.

Other features of the preferred embodiment of the slide-wire assembly of the present invention comprise the provision of a terminal block located on one end of the cylindrical support, and also the provision of a shield for enclosing the slide-wire assembly to prevent stray magnetic or electrical fields from adversely affecting the slidewire. assembly.

The various features of novelty which'characterize this invention" are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects obtained with its use. reference should be had to the accompanying drawing and descriptive matter in which is illustrated and described a preferred embodiment of the invention.

Of the drawings:

Fig. 1 is an elevational view of the slide-wire assembly of the present invention with the, cover thereof removed;

Fig. 2 is a vertical, sectional view of the slidewire assembly;

- Fig. 3 is a detail sectional view of the cable drum of the slide-wire assembly taken substantially along the line 8I of Fig. 2;

Fig. 4 is a bottom view of the slide-wire assembly with the cover thereof removed; and

Figs. 5, 6, 7, and 8 are diagrammatic views showing the manner in which the slide-wireand collector elements are secured to the slide-wire assembly.

As previously described, the novel slide-wire assembly of the present invention iswell adapted 9 use in electronic self-balancing P Wills patent.

ometric measuring and/or controlling app ratus of the type disclosed in the aforementioned As shown in said patent, such apparatus advantageously comprises a potentiometric network including a slide-wire resistance assembly consisting of a slide-wire resistance element, a collector bar elementand a sliding contactor in bridging engagement with said elements and adjustable therealong. The output of the potentiometric network is determined by the position of the slide-wire contactor along the slidewire element, and this output is connected in series with the unknown voltage to be measured in the input circuit of converting means which are operative to produce an alternating voltage signal representative of the difference between the potentlometric output and unknown voltages. This alternating voltage signal is then amplified by suitable amplifying means included in the apparatus, and is utilized in its amplified form to control the motor-drive portion of the apparatus which in turn'controls the speed and direction of rotation of a reversible follow-up or rebalancing motor which forms a part of the apparatus. said motor is suitably coupled to the aforementioned slide-wire contactor, and the apparatus is so constructed and arranged as to cause the rebalancing motor to impart to the slide-wire contactor what ever motions are necessary in order to maintain the apparatus balanced at all times, with the potentiometric network output voltage equal in magnitude and opposite in direction to the unknown voltage to be measured. Accordingly, the position of the slide-wire contactor along the slide-wire resistance element provides a continuous measure of the magnitude of the unknown voltage.

The slide-wire assembly of the present invention, in a form which-renders it well suited for use in apparatus of the above-described type, is designated in Figs. 1 through 8 of the present application by the reference character l9; Broadly, the slide-wire assembly l9 includes; a slidewire resistance element 49, a collector bar element 49, and -a cooperating-sliding contactor 49. As will be described hereinafter, the slide-wire assembly also includes means adapted to be driven bythe rebalancing motor oi-the associated apparatus and operative,':when "so driven, to position the contactor 49 along the elements 49 and '49 as necessary to maintain said apparatusina balanced condition. The details of construction of the slide-wire assembly l9 of the present invention will now be described. As shown, the assembly includes a cylindrical core-499 upon which the slide-wire resistance element 49, the collector bar element 49, and a resistance winding 94 are mounted. The core 499 is preferably made of ceramic material, such materialbjeingagood insulator and also havinga temperature-coefllcient of expansion similar tothat'oftheslide-wire resistance and collector bali:v flhe'inner-surface of the cyllndrlcal core. 499' is provided with'a shoulder 49l which isabutted by a plate 492. The plate 492 also abuts a shoulder 494 formed on a sleeve 499,

spect to the plate 929 is prevented. A rigid structure is thereby provided.

Figs. 5, 6, '7, and 8 show the manner in which the slide-wire 49 and the collector bar .49 are socured to the core member 499. The slide-wire 49, preferably made of manganin wire, is space wound on an insulated wire 41 such as Former insulated manganin wire. The right-hand end of the slide-wire 49, as viewed in Fig. 5, is solderedto the wire 41 at a point thereon from 'which the'insulation is removed to provide an electrical connection between the slide-wire 49 and the wire 41 at said point. A lead wire "I is flattened at one end as shown at 492 in Figs. 5, 9 and 7, and this flattened end is wrapped around the other end of the slide-wire 49 and is soldered thereto to form an electrical connection between the slide-wire 49 and the lead wire 49f. The slide-wire 49 is wrapped around the core member 499 and is located on the core member 499 in a groove. The wire 41 extends through holes in the core member 499, and washers 492 and 499, soldered to the wire 41, hold the wire 41 and hence the slide-wire 49 on the core member 499. In a like manner the lead wire 49f is held in place by a washer 494 soldered to the leadwire 49!.

The collector bar is formed by space winding the manganin wire 49 around a manganin wire 49. Here, the wire 49 is not provided with insulation, so that the wires 49 and 49 are electrically conductive throughout their lengths. Thecollector bar is also wrapped around the core member 499 in agroove which is parallel withflthe groove containing the slide-wire 49. The wire 49 extends through openings in the core member 499, and washers 499 and 499,,soldered to .the wire 49, hold the wire 49 and hence the wire 49. in position on the core member 499. The core member 499 is also provided with a circumferene tial groove receiving the resistance winding 94. The wire 49 of the collector bar and the wires 4" and 41 of the slidea-wireextend upwardly,

through an opening in the mounting plate 929 to terminals 9|, 9!, and 99, respectively, carrled'by a terminal block 99. The terminals 9|, 9!, and 99, which are adapted to be connected to suitable points in the. potentiometric network of the associated apparatus, are held in-spaced relation by a spacer member 499 made of insulating material, and are clamped in place by means of 18cm .1 m er 499. also madeof insulating material,

By winding the slide-wire 49 on the wire 41 in the manner just described, a loop is not formed and, therefore, there is no tendency for the slidewire to pick up any stray electrical currents. Due to the fact that the leads between the slide-wire and collector bar and the terminals 9|, 9! and 99 are extremly short, there is no tendency for these leads to pick up stray electrical currents. The

resistance winding 94 is connected across the wires 41 and 49l by soldering as illustrated in Fig. 2., The resistance of the winding 94 is so selected that the total resistance of the slide-wire assembly is a predetermined value, to provide 1|.

universal slide-wire assembly.

The upper and lower ends of the sleeve 499 are provided with bushings- 999 and 999, respectively,

.and rotatably mounted in these bushings is a shaft 994 provided with a shoulder adjacent its' upper end to limit downward movement thereof. A collar 999 is secured to the lower end of the shaft 994 by means of a pair of set screws 999 0011- tacting flattened portions on the shaft 994. The I99 therefore rotates with the shaft 994.

stem .to' the. collar m for rotation therewith lean arm 501 provided with a radial slot 500 and a circumferential slot 509. Rotatably mounted on the collar 505 between the arm 501 and the collar 5 is another arm H0. The arm 519 carries .an eccentric 5 operating in the radial slot 000 so that the arm "0 may be angularly I comprises a cylindrical portion located in the vertical slot 5" and a shaft 5l9 engaging the inner surface of the spring member 5 l 4. Preferablythe contactor 45 is made of silver which is softer than the manganin wire forming the collector .bar and slide-wire "and 49, respectively. Any

wear that takes place will take place on the contactor 45 and not on the slide-wire and the collector bar. When the shaft 504 rotates to cause the contactor 45 to slide along the slide-wire andthe collector .bar, the contactor 45 moves upwardly and downwardly in the vertical slot 510. and this upward and downward movement causes rotation of the contactcr 45 about its shaft 5i9.

Accordingly, as the shaft 504 is rotated, a new I contact surface on the contactor 45 is continuously presented to the slide-wire and the collector bar. This assures a good wiping contact at all times.

The various parts of the slide-wire assembly ii are enclosed in a case 5 which is held against the bottom surface of the mounting plate 920 by means of spring arms 522 carried by apertured ears 5. The case 521 not onlyprotects the parts of the slide-wire assembly I from dirtand corrosive'atmospheres but also acts as a shield to prevent stray electrical-currents from affecting-the operation of the slide-wire assemblyr-If desired, the cover 52! may be filled with 095-. As seen in Figs. 2 and 9. the undersurface- 532. The cable then passes over the pulleys and a second cable drum. not shown, and then returns to the first part Ill being wrapped around the remaining grooves 53! thereof. Said second cable drum is adaptedto be rotated byv the rebalancing motor of the apparatus, not shown, whereby said motor imparts motion to the cable drum 49 through the cable 44.

The second end of the cable is also provided with a bushing 54! suitably secured thereto; and this bushing 54! is inserted in a hole 540 formed in the second part 533. The cable 44 lies in a groove 539 also formed in the second part 509. By rotating the part 530 with respect to the first part 59!, the effective length of the cable' 44 is varied and, therefore, the tension of the cable 44 may be adjusted to the desired value. The screw 585 is then tightened to clamp the second part 593' in a fixed position with respect to the first part 53!. Accordingly, the two-part cable drum 49 in addition to anchoring the ends of the cable 44 and driving the slide-wire It also forms a means for adjusting the tension of the cable 44. In order to facilitate this adjustment, the shoulder on the shaft 504 is provided with a hole 541 which lines up with a hole provided in the frame of the associated potentiometer apparatus, as shown at 548 in Fig. 11 of my aforementioned patent, when the slide-wire assembly is in the zero position. A pin may then be inserted 7 through the said hole 548 into the hole 541 for ollfor immersing the slide wire assembly there in, and this proceduremay'be particularly licev extremely s irable if the instrument-sis used in corrosive atmospheres.

The upper end of the arm 5"! is provided with a pointer 525 which cooperates with a relatively stationary pointer 529 carried by-a bracket 521.

The bracket 52'! is provided withslots520, and

screws 529extending through the slots 529 adjustably secure the bracket 521 tothe underside on the mounting plate 020. When the asso-; elated instrument is calibrated at the factory for zero position, the marker on the pointer 520 is moved to line-up with" the marker on the pointer I25, whereafter, the bracket 521 isclamped in place by thejscrewsy'529. Accordingly, the position of the marker '5" indicates the zero position according to the factorycalibration so that when the slide-wire assembly is disassembled for cleaning or repair P rposes it can be readily restored,

to'theoriglnal zero factory calibration.

Acable drum 43 which operates the slide-wire assembly I0 is formed of two parts. The first 7 holding the lower member 59! of the cable drum 43 stationary in the zero position while the upper member 533 is being adjusted to secure the proper tension in the cable 44.

In assembling the instrument, the slide-wire assembly is ;moved to the zero position and is held in that position by the pin extending through the holes 541 and 540. The second and unillustrated'cable drum of the associated apparatus is then moved to the zero position, and the cable 441s then wound in the grooves of the lower member "53l .1p...to two. grooves from the top, passed over the aforementioned"pulleys and second cable drum, and then wound in the top groove of the lower member 53l and secured in the upper member 533. The upper member 503 is then rotated to secure the proper tension in the cable 44. The cable 44 is then secured to said second cable-drum. This method of assembly accurately positions the slide-wire assembly IS with respect to said second cable drum.

- andproperly adjusts the cable tension. It will be noted that the bottoms of the grooves 592 are fiat so that variations in the thickness of the cable 44' will not materially affect the effective length of the cable as would grooves were V-grooves.

The lower'member MI is provided with a pair of arcuate eccentrically located holes 90l',.a cut 902 connecting the holes and a cut 9-03 connecting the cut 902 to the periphery of the lower member. These holes and cuts extend entirely through the lower member 53!. The .cut 909 is provided with a double taper hole 904 in which is located a conical wedge 905 anda screw 900. 'By

tightening the screw 906 in the conical wedge 905, the conical wedge cooperates with the tabe the case if the 7 persd hole ill to spread the cut III,this being permitted by the holes III and the cut III. This increases the diameter or the circumference of the lower member III. By properly adjusting the screw III, the effective diameter or circumference of the cable drum is adjusted. whereby the correct amount of movement of the slidewire contactor lI with respect to a predetermined movement of the cable ll may be obtained. The upper member III is provided with a radial hole I" so that the screw III may be accessible for adjustment purposes.

The screw III is provided with a longitudinal hole Ill .which opens into holes Ill and Ill formed in the shaft Ill. The lower end of the hole IlI communicates through a radial opening I with the chamber in the, sleeve I between the bushings III and III. Thueholes and openings are provided for the purpose of supplying oil for lubricating purposes to the bushings II: and III.

While, in accordance with the provisions of the statutes, I have illustrated and described the best formvof the invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention as set forth in the appended claims, and that in some cases certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is: V

1. In a slide-wire assembly, the combination of, a support, an insulated wire carried by said support, a bare wire space wound on said insulatcdwire, a bare wire carried by saidisupport and spaced from and parallel to the insulated wire and of substantially the same gage as the insulated wire, a bare wire space wound on said second mentioned bare wire and electrically conductive throughout its length with the said bare wire and of substantially the same gage as the bare wire which is space wound on the insulated wire, a contact bridging the space wound bare wires and relatively movable with respect thereto, a terminal block having three terminals located on the support adjacent one end of the wires, a connection between one of the terminals and the near end of the insulated wire, a connection between another of the terminals and the near end of the bare wire which is space wound on the insulated wire, a connection between the opposite 'ends of the insulated wire and the bare wire space wound thereon, and a connection between the other terminal and the near end of the bare wire upon which is space wound the other bare wire.

2. In a slide-wire assembly, the combination of, a support, an insulated wire carried by said support, a bare wire space wound on said insuwire, and a contact bridging the space wound bare wires and relatively movable with respect thereto. said support being provided with openlugs and the ends of the spaced parallel wires a,sss,ssc

extending through the openings and being sscured therein to hold all of the wires in place on the support.

' 3. In a slide-wire assembly, the combination of, a cylindrical support formed of insulating material, a resistance wirev helically wound on the exterior surface of the cylindrical support, a collector wire helically wound on the exterior surface of the cylindrical support and spaced from and parallel to the resistance wire, a rotary shaft concentrically mounted with respect to said cylindrical support, means for rotating the shaft, an arm carried by the shaft and extending along the exterior surface of the cylindrical support, an adjustable linkage connecting said arm to said shaft whereby said arm can be adjusted relative to said shaft, a slot in said arm parallel tcjthe axis of the cylindrical support, and a roller rolling in said slot and bridging the resistance wire and-the collector wire.

4. In a slide-wire assembly, the combination of, a cylindrical support formed of insulating material, a resistance wire helically wound on the exterior surface of the cylindrical support, a collector wire helically wound on the exterior surface of the cylindrical support and spaced from and parallel to theresistance wire, a rotary shaft concentrically mounted with respectto said cylindrical support, means for rotating the shaft,

an arm adjustably carried by the shaft and extending along the exterior surface of the cylindrical support, a slot in said arm parallel to the axis of the cylindrical support, a roller rolling in said slot and bridging the resistance wire and the collector wire, a pointer carried by said arm, and a pointer adjustably carried by said support cooperating with the first mentioned pointer to indicate the zero position of the slide-wire assembly.

5. In a slide-wire assembly, the combination of, a cylindrical support formed of insulating material, a resistance wire helically wound on the exterior surface of the cylindrical support, a collector wire helically wound on the exterior surface of the cylindrical support and spaced from and parallel to the resistance wire, a rotary shaft concentrically mounted with respect to said cylindrical support, means for rotating the shaft, an arm carriedby the shaft and extending along the exterior surface of the cylindrical sup r a slot in said arm parallel to the axis of the cylindrical support, a roller rolling in said slot and bridging the resistance wire and the collector wire, and'a shield enclosing the slide-wire assembly to prevent stray electrical fields from affecting the slide-wire assembly.

, 6. In a slide-wire assembly, the combination of, a cylindrical support formed of insulating material, an insulated wire helically wound on the exterior surface of the cylindrical support, a bare wire space wound on said insulated wire, a bare wire helically wound on the exterior surface of the cylindrical support and spaced from but parallel to the insulated wire and of substantially the same gage as the insulated wire, a bare wire space wound on said second mentioned bare wire and electrically conductive throughout "its length with the said bare wire and of substantially the same gage as the bare wire which is'space wound on the insulated wire, arotary shaft concentrically mounted with respect to said cylindrical support, an arm adjustably carried by the shaft and extend ng along the exterior surface of the cylindrical support, a slot in said arm parallel to the axis of the cylindrical support, a roller rolling in the slot and bridging the space wound bare wires, aterminal block having three terminals located on one end of the cylindrical support adjacent one end of the wires, a connection between one of the terminals and the near end of the insulated wire, a connection between another of the terminals and the near end of the bare wire which is space wound on the insulated wire, a connection between the opposite ends of the insulated wire and the bare wire space wound thereon, and a con- REFERENCES CITED UNITED STATES PATENTS"II"I Number Name 4 Date 1' 1,744,592 Terpening Jan/21,1930 1,996,175 Schellenger 1." Apr. 2, 1935; 2,122,370 Harrisonet-al .Q June 28,1938 

